David's Blackbird 7

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bzrse7en
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Joined: Thu Apr 23, 2009 3:40 pm
Location: Rolleston Canterbury

Re: David's Blackbird 7

Post by bzrse7en » Sat Feb 04, 2017 8:55 am


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feckn7
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Re: David's Blackbird 7

Post by feckn7 » Sat Feb 04, 2017 10:29 am

If you're running an escort axle the best ratio you can get is the 3.54 - again quite hard to get and usually quite pricey.
As I was getting the sierra axles shortend the engineer suggest I should use the Toyota RAV 4 diff as they are 2.91 and easier to get

Thanks for the heads-up bzrse7en

David

Mauntinbyka
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Re: David's Blackbird 7

Post by Mauntinbyka » Sat Feb 04, 2017 5:20 pm

If you're running an escort axle the best ratio you can get is the 3.54
This is an interesting comment. Why do you think this? Is it because it gives more legs to first gear so that it is more useable at lower speeds? I've got a 3.54 diff and thought it was going to be a bit highly geared.

Terry

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feckn7
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Re: David's Blackbird 7

Post by feckn7 » Sat Feb 04, 2017 5:51 pm

By best, I mean best for a bike engined car.
A bike engine is quite different to a car engine - although the engine (in my case) revs to almost 11,000 it's not the same as a car engine revving to 11,000
In my case 6th gear is 1.028:1 ( where as cars 5th gear is usually overdriven 4th being 1:1) plus there is a primary ratio of 1.596:1 so 11,000 equals 6704 rpm into the diff.
With my car at present 1st gear will give ~85K at redline but 100kmh in 6th is around 5700rpm ( a bit busy) it also gets to the redline in 1st very quickly. I can quite easily take off in 2nd and still beat most away from the lights - the only thing that have matched me away from the lights are 1000cc sports bikes
A 3.38 diff would mean almost 100k in 1st but 100kmh would be ~4800 which is more relaxed.

David

bzrse7en
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Re: David's Blackbird 7

Post by bzrse7en » Sat Feb 04, 2017 5:54 pm

Yea, i went from a 3.62 to a 3.9 sierra diff with a 4age 20v and 13" rims, make that little 4 pot screem i say. I thought the 4.1 was a good choice. No right answer here I suppose

Talkiet
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Re: David's Blackbird 7

Post by Talkiet » Sat Feb 04, 2017 9:10 pm

I haven't tried anything else but the power of that little 20V 4age + the 3.9 LSD is pretty crazy. With good tyres it can do 0-100 in 4.25sec. I don't need anything faster :-)

My 1990 CRX SiR has some crazy (factory) ratio - It's doing about 4000RPM at 100k. Kinda nuts for a production car.

N

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